KVNKVN

VVLBI LBI EExtragalactic xtragalactic CoCompact mpact RRadio adio SSource ource

SSurvey urvey Lee, Sang-SungLee, Sang-Sung 2009EastAsiaVLBIWorkshop2009EastAsiaVLBIWorkshop

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CollaborationCollaboration

Initiated by collaboration btw VERA and KVN VERA

• Mareki Honma

KVN• Bong Won Sohn

• S. Lee

Accelerated by motivation from Yuri Y. Kovalev (MPIfR) Leonid Petrov (GSFC/NASA)

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ContentsContents

IntroductionProject: VECoRSS

Goals Motivations Substance Plan

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Active Galactic Nuclei (AGN)Active Galactic Nuclei (AGN)

Marscher 2005Marscher 2005

Observables:Observables:

Flux density (Flux density (SS))Angular Size (Angular Size (θθFWHMFWHM))

Apparent jet speed (Apparent jet speed (ββappapp)) Brightness Temperature Brightness Temperature TTbb

Observables:Observables:

Flux density (Flux density (SS))Angular Size (Angular Size (θθFWHMFWHM))

Apparent jet speed (Apparent jet speed (ββappapp)) Brightness Temperature Brightness Temperature TTbb

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Brightness TemperatureBrightness Temperature

Brightness temperature:

A temperature that a source should have as if it was a black body to radiate a specific intensity

* Gaussian pattern of brightness distribution* Source rest frame

Inverse Compton limit:

Whenever Tb > 1012 K, inverse Compton scattering of radio photons dominates, and most of the energy will be radiated in X-ray. (Kellermann & Pauliny-Toth 1969)(Kellermann & Pauliny-Toth 1969)

Equipartition limit:

Sources radiate at Tb ~ 5 x 1010 K when energy densities in relativistic particles and magnetic fields are in equipartition. (Readhead 1994)(Readhead 1994)

High-resolution VLBI surveys enable to statistically study the brightness High-resolution VLBI surveys enable to statistically study the brightness temperatures of compact radio sources and temperatures of compact radio sources and to test the theoretical models of to test the theoretical models of relativistic outflowsrelativistic outflows (e.g., Marscher 1995). (e.g., Marscher 1995).

High-resolution VLBI surveys enable to statistically study the brightness High-resolution VLBI surveys enable to statistically study the brightness temperatures of compact radio sources and temperatures of compact radio sources and to test the theoretical models of to test the theoretical models of relativistic outflowsrelativistic outflows (e.g., Marscher 1995). (e.g., Marscher 1995).

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Relativistic effects and lower limitRelativistic effects and lower limit

Relativistic effects:

Radiation emitted from a jet component moving at a velocity of with an angle to the line of sight can be Doppler boosted.

Doppler factor

Apparent jet speed

Lower limit of Tb:

Minimum resolvable size dmin

a,b: axes of restoring beamSNR: signal-to-noise ratio : weighting function

When d < dmin, the lower limit of Tb should be estimated with d = dmin.

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VLBI Core and its opacity effectVLBI Core and its opacity effect

Lobanov (1996)Lobanov (1996) • VLBI core is located at a region where in the jet.

• Under the equipartition condition, the absolute position of the VLBI core rr is related to the total radiated synchrotron luminosity LLsynsyn

• VLBI core is located at a region where in the jet.

• Under the equipartition condition, the absolute position of the VLBI core rr is related to the total radiated synchrotron luminosity LLsynsyn

1

In order to investigate the physics of compact radio jets in sub-parsec scale In order to investigate the physics of compact radio jets in sub-parsec scale regions, we need to observe them at higher frequencies with high resolution regions, we need to observe them at higher frequencies with high resolution (high resolution VLBI survey). (high resolution VLBI survey).

In order to investigate the physics of compact radio jets in sub-parsec scale In order to investigate the physics of compact radio jets in sub-parsec scale regions, we need to observe them at higher frequencies with high resolution regions, we need to observe them at higher frequencies with high resolution (high resolution VLBI survey). (high resolution VLBI survey).

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FS43:FringeSurvey

at 43GHz

VIS43:VLBI Imaging Survey at 43GHz

pFS43:pilotFringeSurveyat 43GHz

Project: VECoRSSProject: VECoRSS

VECoRSS: VLBI Extragalactic Compact Radio Source Survey

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ICRFICRFICRFICRF

CalibratorCalibrator

43GHz43GHz

CalibratorCalibrator

43GHz43GHz

VECoRSS: GoalsVECoRSS: Goals

TrainingTraining

VLBI expertsVLBI experts

TrainingTraining

VLBI expertsVLBI experts

PC-scale structurePC-scale structureof compact radio of compact radio

sourcessources

PC-scale structurePC-scale structureof compact radio of compact radio

sourcessources

InternationalInternational

collaborationcollaboration

InternationalInternational

collaborationcollaboration

KVNKVNKVNKVN

NASANASA

GSFCGSFC

NASANASA

GSFCGSFCMPIfRMPIfRMPIfRMPIfR

VERAVERAVERAVERA

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Large VLBI surveysLarge VLBI surveys

*sub-sample.**VERA 22 GHz survey is done in collaboration withH. Kobayashi, T. Jike, M. Honma, K.M. Shibata, T. Hirota.

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VECoRSS: MotivationVECoRSS: Motivation

Only a few 100 sources have been observed/imaged at 43 GHz for geodetic/astrometric purpose (VLBA, Lanyi et al).

A KVN/VERA fringe survey at 43 GHz should be considered for VERA, KVN, VSOP-2, etc. VERA: needs a full list of extragalactic calibrators at 22/43 GHz for

dual-beam Galactic astrometry. (e.g., VERA fringe survey at 22 GHz; Petrov et al 2007, Full sky VERA fringe survey at 22GHz ongoing; Petrov et al.)

KVN: needs the list of calibrators at 22/43 GHz for multi-freq. phase-referencing observation at 22/43/86/129 GHz.

VSOP-2: needs preparatory surveys for identifying suitable radio sources for phase referencing observation at 8/22/43 GHz (VSOP-2 pre-launch survey at 43 GHz).

A follow-up VLBI imaging survey at 43 GHz with a complete sample of compact radio sources is required to study compact AGN jets.

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ppFS43: FS43: pilotpilot Fringe Survey at 43 GHz Fringe Survey at 43 GHz

pFS43 (2009) : A 24-hr pilot observation of ~ 270 compact radio sources out of 550 candidates selected (with VERA+KVNYS). Goals: to answer the following questions;

• What is the baseline sensitivity of VERA (+KVN) at 43 GHz : ∆SVERA. Expected value ∆SVERA ~ 150 mJy (VERA team, priv. comm.)

• How to schedule the fringe survey?• How to fringe-fit?• What are the criteria for selecting the candidate sources?• What are the amplitude calibrators?• How often the amplitude calibrators should be observed?• What will be the accuracy of amplitude calibration?• What is maximal integration time?

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ppFS43 - proposalFS43 - proposal

Source selection criteria: 270 out of 550 candidates• Correlated flux density of Sc ≥ 300 mJy on baselines of 170 ~ 250

Mλ at 8 GHz based on the catalogs of VCS1-6 and ICRF• Compactness of Sc/SVLBA ≥ 0.4 at 8 GHz• Detected sources in 3mm VLBI survey (Lee et al. 2008)• Correlated flux density of S22 ≥ 500 mJy on baselines of 100 ~ 200

Mλ at 22 GHz base on the VERA Fringe survey at 22 GHz (Petrov et al. 2007)

Amplitude calibration:• Amplitude calibrator : 20 sources from the Blazar (2-3 months)

monitoring program at 43GHz (Marscher et al. Boston Univ.) Observation:

• Six 4-hour observations with dynamic scheduling• Each source will be observed for one/two scan(s) of 2-min

duration.• Amplitude calibrator should be observed every 20 min.

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Selected sourcesSelected sources

270 objects selected for the pilot observations Group1 (90)Group1 (90) : Sc > 500 mJy, Sc/SVLBA ≥ 0.4

Group2 (133)Group2 (133) : 500 mJy ≥ Sc ≥ 300 mJy, Sc/SVLBA ≥ 0.4

Group3 (47)Group3 (47) : Sc < 300 mJy, Sc/SVLBA ≥ 0.4

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Sky distributionSky distribution

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Observed sources at 1Observed sources at 1stst epoch epoch

Preliminary detection rate

40% with FRING(AIPS)

70% with VEDA

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Observed sources at 1Observed sources at 1stst and 2 and 2ndnd epochs epochs

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FS43: Fringe Survey at 43 GHzFS43: Fringe Survey at 43 GHz

FS43 (2010-2011) : Survey observations with EAVN-Array43 (VERA, KVN, Nobeyama, Kashima) Sources with expected Sc > ∆SVERA

Each source observed for one or two scans. The first whole-sky fringe survey at 43 GHz in Northern

hemisphere. Spectral index (at 22-43GHz) obtained from KVN data.

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East Asian VLBI Network (EAVN)East Asian VLBI Network (EAVN)

EAVN-Array-QEAVN-Array-Q (so called) : KVN(3x21m) + VERA(4x20m) + Kashima(34m) +

Nobeyama (45m)

EAVN-Array43

0.7 mas@43GHz

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VIS43: VLBI Imaging Survey at 43 GHzVIS43: VLBI Imaging Survey at 43 GHz

VIS43 (2012-2013) : A follow-up VLBI imaging survey with a complete sample (EAVN-Array-Q + VLBA) A complete sample based on the results of FS43 Improve the data base of AGN VLBI images at 43 GHz A good database for International Celestial Ref. Frame (ICRF-ext2) Statistical study of intrinsic properties of relativistic jets. Resolution of the global VLBI survey at 43 GHz will be matched with

that of VSOP-2 at 22 GHz• Comparison of structural information and morphology at matched

resolution

• Comparison of Tb distribution at 22/43 GHz

– To see if there is any difference.

– To see if the difference is coming from jet stratification or opacity effect.

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Statistical study of compact jetsStatistical study of compact jets

Change of Tb in a jet => acceleration/deceleration of relativistic jets

Change of Tb

Tb increases up to

20 GHz and then starts to decrease

At 86 GHz, Tb are

systematically low.

Change of Tb

Tb increases up to

20 GHz and then starts to decrease

At 86 GHz, Tb are

systematically low.

A VLBI imaging survey at 43 GHz is required to fill this gap to confirm

the possible trend of Tb

A VLBI imaging survey at 43 GHz is required to fill this gap to confirm

the possible trend of Tb

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Change of Change of TTbb in a jet in a jet

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Change of Change of TTbb in a jet in a jet

(Vlahakis & Koenigl (2004)

r [pc]

Compact jets may be accelerated by magnetohydrodynamic (MHD) forces.

Compact jets may be accelerated by magnetohydrodynamic (MHD) forces.

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ICRF-ext2

VECoRSS: PlanVECoRSS: Plan

2009

2010

A completesample of calibrators

2011

2012

2013

pFS43

VIS43

FS43

VIS43

VSOP-2

VSOP-2

VERAVERAFS43

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Thank you!